Slides for discussion of The Living World, 7th edition chapter 37, adapted from a compilation by Amy.

1. Behavioral
Ecology

2. How evolution
shapes behavior

3. Optimality

4. Organisms behave to
maximize benefit and minimize
cost

5. Optimal Foraging
maximize nutritional benefits
minimize energetic/survival costs

6. Zach, 1978

7. Crows generally fly
5 meters high
Zach, 1978

8. Higher than 5 meters does not increase
the chance of the shell breaking
Benefits < Costs
Zach, 1978

9. Territory

10. Territory
Benefits: exclusive access to food,
mates
Costs: energy required to defend

12. Reproductive
Behavior

13. Optimized Reproduction
maximize offspring
minimize energetic/survival costs

14. Energetic/survival costs are typically
unequal between males and females
“Battle of the vs
Sexes”

15. Mate
Choice

16. Parental Investment Theory
The sex with the most energetic costs from parenting
will be more selective

17. Which sex has
higher parental costs?

18. Birds
female produce large eggs
and may lay 50 to over 100%
of their body weight each
season

19. Mammals
only females can become
pregnant and lactate

20. Generally, females invest more
in eggs than males do in sperm

21. Females are usually more selective

22. Mate Choice causes
Sexual Selection
Intrasexual: traits that give a
competitive advantage
Intersexual: traits that are preferred
by the chooser sex

23. Intrasexual Selection

24. Intersexual Selection

25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Number of mates Fig. 37.12
5
0
140 150 160
Number of eyespots in tail feathers

26. Mating systems Jacana
Polyandry: multiple males
Polygyny: multiple females
Promiscuous: multiple males & females
Monogamy: one male, one female
Elephant seal Dunnock
Black vulture

27. Clumped food (fruit tree): Polygyny/Polyandry
Random/uniform food (insects): Monogamy

28. Social
behavior

29. From simple social groups………

30. …. To complex societies

31. Altruism

32. Behavior that benefits others
at a cost to the individual

33. Cost may be minor…

34. …or extreme!

35. Optimality
maximize benefit
minimize cost
So how could altruism evolve?

36. Reciprocity

37. “You scratch my back,
I’ll scratch yours.”

38. Vampire bats

39. Benefit = survival (as a recipient)
Cost = small amount of food loss
(as a donor)
Benefit > Cost in the long term

40. Kin Selection

41. Helping your relatives

42. "Would I lay down my life
to save my brother?
No, but I would to save two
brothers or eight cousins.”
-J.B.S. Haldane
Siblings: share 1/2 of your genes
Cousins: share 1/8 of your genes

43. Fig. 37.17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Probability of helping (percent) 100
80
60
40
20
0
0 1/8 1/4 1/2
(cousin) (half-sibling) (full-sibling)
Degree of genetic relatedness

44. Belding’s ground squirrels

45. Benefit = protect relatives
who share genes
Cost = increased predation risk to self
Benefit > Cost if relatives near by

47. Communication

48. Fig. 37.15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
8 8
7 7
Frequency (kilocycles
Frequency (kilocycles
6 6
per second)
per second)
5 5
4 4
3 3
2 2
1 1
0 0
0.5 seconds 0.5 seconds
Eagle Leopard
(a) (b)
a: © S. Osolinski/OSF/Animals Animals-Earth Scenes